Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add tranhieutt/software_development_department --skill vertical-slicinggit clone --depth 1 https://github.com/tranhieutt/software_development_departmentWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/tranhieutt/software_development_department/vertical-slicing)<a href="https://agentmods.dev/skills/tranhieutt/software_development_department/vertical-slicing"><img src="https://agentmods.dev/badge/skills/tranhieutt/software_development_department/vertical-slicing/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/tranhieutt/software_development_department/vertical-slicing"><img src="https://agentmods.dev/badge/skills/tranhieutt/software_development_department/vertical-slicing.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00022 | $0.00698 |
| Opus 5 | $0.00011 | $0.00349 |
| Sonnet 5 | $0.00004 | $0.00140 |
| Haiku 4.5 | $0.00002 | $0.00070 |
Grade A, and why
vertical-slicing scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 8d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 71 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Skill: /vertical-slicing
Use this skill when planning complex fullstack features to ensure delivery by user-value units rather than technical layers.
Vertical slices should not merely cross layers. They should also protect depth: keep complexity concentrated behind small interfaces instead of smearing logic across DB, API, and UI callers.
The Vertical Slicing Workflow
1. Identify the Smallest Value Unit
- Decompose the PRD into slices that represent a functional path.
- Example: Instead of "Authentication System," start with "Login with Email and Password".
Good slice shape:
- Narrow enough to demo or verify independently
- Complete enough to exercise the real seam end-to-end
- Small enough that one RED -> GREEN loop can prove meaningful progress
- Not a horizontal placeholder like "backend groundwork" unless that groundwork is a real prerequisite with its own verification
2. Define the Contract
- Before implementing, the
lead-programmerorbackend-developermust define the API contract. - Document this in a Design Doc or temporary spec.
Prefer contracts that create deep modules: small interfaces with meaningful behavior hidden behind them. If a contract mostly forwards data or mirrors caller complexity, it is probably too shallow.
3. Plan the Slice Tasks
Organize each phase to contain:
- Database/Data Model: Schema changes required for this slice.
- Backend Implementation: Logic and API endpoints.
- Frontend Integration: UI components and API consumption.
- E2E Verification: Test verifying the whole path.
For each slice, also record:
- Blocked by: exact prerequisite slice(s) or
None - Acceptance criteria: observable end-to-end outcomes
- Verification: exact command/check for the slice
- Interface risk: where a shallow seam or pass-through wrapper could appear
4. Implementation Rules
- Do not confuse "deepest" with "lowest layer". Start where the slice creates the strongest behavior seam, then drive outward through the stack.
- Do not move to the next slice until the current one is "Integration Complete".
- If a horizontal change is absolutely necessary (e.g., shared middleware), implement it as a prerequisite phase 0.
- Apply the deletion test to new wrappers and adapters. If deleting the new abstraction would mostly simplify the code instead of reintroducing complexity across callers, the seam is too shallow.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 8d ago First seen · 71 lines · 22 tokens per session scan A 67fb426a984b
vertical-slicing is a skill published in the GitHub repository tranhieutt/software_development_department (72 stars, last pushed 4mo ago), licensed MIT. It adds 22 tokens to every session and 698 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.
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